Brief intro to vertebrates

Question 1

What is the splanchnocranium?

Answer 1

The facial skeleton, formed from neural crest.

Question 2

What is the chondro/neurocranium?

Answer 2

Supports the brain, formed from neural crest.

Question 3

What is the dermatocranium?

Answer 3

The insides and roof of the skull, formed from ectoderm.

Question 4

What are the 2 hypothesis for the relationships of the agnathostomes?

Answer 4

1. Molecular: the hagfish and lampreys are a clade
2. Morphological: the lampreys and gnathostomes form a clade, the hagfish are a sistergroup (as they do not have a notochord).

Question 5

Describe a hagfish.

Answer 5

A carrion feeder. They produce slime and tie themselves in knots during prey capture and predator evasion.

Question 6

One of the hypotheses for the origin of jaws states that they were formed from the anterior-most gill arches. What was this initially an adaptation for?

Answer 6

Improved gill ventilation, not for feeding.

Question 7

In sharks, the teeth are embedded in the jaw bone. True or false?

Answer 7

False: they are embedded in the flesh.

Question 8

What is the jaw articulation in lissamphibia and lepidosaurs?

Answer 8

Meta autostylic: the upper jaw is fused to the skull. The lower jaw is attached via the quadrate and articular.

Question 9

What is the jaw articulation in mammals?

Answer 9

Craniostylic: lower jaw is fused to the braincase via the squamosal and dentary.

Question 10

What are the ‘adductor mandibulae’?

Answer 10

Jaw-closing muscles.

Question 11

What is the jaw articulation in fish?

Answer 11

The hyomandibular attaches the lower jaw to the braincase.